Flexible scaffold for supporting sliding molds or climbing molds used for the erection of concrete structures

ABSTRACT

A sliding or climbing mold for the erection of concrete structures the horizontal cross-section of which varies vertically comprises a scaffold system composed by a plurality of flexible scaffold units. Each such unit consists of two pivotably interconnected and intersecting rods or the like separated by yokes supporting the mold. First and second hydraulic jacks acting in the vertical and horizontal directions, respectively, accomplish the vertical movement of the scaffold system and contribute to the change of the horizontal size thereof. A spoke assembly connected to the scaffold system and comprising substantially radially and horizontally located spoke wires is used for variation of the horizontal shape of the scaffold system. A number of replaceable templets are designed for variation of the horizontal shape of the scaffold system and of the effective length of the spoke wire so as to synchronize the movements in vertical and horizontal direction.

United States Patent Svensson et al.

[54] FLEXIBLE SCAFFOLD FOR SUPPORTING SLIDING MOLDS OR CLIMBING MOLDS USED FOR THE ERECTION OF CONCRETE STRUCTURES [72] Inventors: Sven-Erik Vllhelm Svensson, Norrbyvagen 39, 141-43 I-Iuddinge, Sweden; Ernii Jozef Thoma, Koszta .I.u.l., Budapest XII, Hun- B [22] Filed: Sept. 3, 1970 [21] Appl.No.: 69,379

[30] Foreign Application Priority Data Sept. 8, 1969 Sweden ..12380/69 [56] References Cited UNITED STATES PATENTS 3,521,336 7/1970 Rohlf ..25/131 SA [151 3,659,978 51 May 2,1972

Primary Examiner-J. Spencer Overholser Assistant Examiner-Dewalden W. Jones Attorney-Fred C. Philpitt [5 7] ABSTRACT A sliding or climbing mold for the erection of concrete structures the horizontal cross-section of which varies vertically comprises a scaffold system composed by a plurality of flexible scaffold units. Each such unit consists of two pivotably interconnected and intersecting rods or the like separated by yokes supporting the mold. First and second hydraulic jacks acting in the vertical and horizontal directions, respectively, accomplish the vertical movement of the scaffold system and contribute to the change of the horizontal size thereof. A spoke assembly connected to the scaffold system and comprising substantially radially and horizontally located spoke wires is used for variation of the horizontal shape of the scaffold system. A number of replaceable templets are designed for variation of the horizontal shape of the scaffold system and of the effective length of the spoke wire so as to synchronize the movements in vertical and horizontal direction.

12 Claims, 21 Drawing Figures Patented May 2, 1972 5 Sheets-Sheet l Patented May 2, 1972 5 Sheets-Sheet 2 Fig.2

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Patented May 2, 1972 5 Sheets-Sheet 5 HHIIHI 1 Patented May 2, 1972 5 Sheets-Sheet 4.

ILI Ill Ill-I'll lllu l|| l Lr ||||l- FLEXIBLE SCAFFOLD FOR SUPPORTING SLIDING MOLDS OR CLIMBING MOLDS USED FOR THE ERECTION OF CONCRETE STRUCTURES When erecting concrete structures of relatively great height and of varying horizontal cross-section it has become successively usual to rely on the sliding mold technique. Especially when the cross-sectional area of the structure is considerable it has proved advantagous to have the sliding molds supported by some type of flexible scaffold establishing and maintaining the desired exact horizontal cross-section of the concrete structure at different vertically spaced levels. It is necessary for such a scaffold to be continously varied, either diminished or enlarged, in synchronism with the raising of the mold. By way of example, in concrete structures of circular cross-section, such as chimneys, television towers and the like, any vertical displacement of the scaffold and of the mold shall correspond to a decrease or an increase of the diameter in full agreement with the geometric shape of the concrete structure defined by static calculations. A scaffold of the type here at issue is composed by scaffolding units the number of which vary in different cases in response to the diameter of the concrete structure. The necessary continous modification of a scaffold consisting of such units is considerably facilitated if all the means for effecting that modification, or change, act in the same direction. This is the case e. g. at scaffolds of the type where the units are substantially constituted by tworods or frames which are of equal length and in their central point of intersection are pivotably interconnected. The pivot axis is generally substantially horizontal and all of the units, which looked upon individually could be described as having the shape of a pair of scissors, are interconnected to a scaffold assembly of polygonal horizontal cross-section, the interconnection of the units being formed by pivots at the ends of the rods so that the sides of the polygon may be varied by variation of the angle of intersection between the two rods making up any such unit. In a scaffold designed in that way the means, or forces, respectively, causing the change of the sides of the scaffold can be arranged to act vertically. It is general practice to have the yokes supporting the sliding mold proper secured at the points of interconnection of the units.

In most cases the vertical displacement of the scaffold and the sliding mold carried thereby is effected by means of hydraulic jacks, all such jacks being connected to a common central power source, generally a hydraulic pump. For that reason it is practical to use hydraulic apparatus also for the purpose of varying the configuration of the scaffold, since such an apparatus can be powered by the same hydraulic source. If the means for varying the configuration of the scaffold above referred to are disposed so that they act vertically and are constituted by e.g. vertical spindles, it is suitable to mount the other hydraulic means so that the forces exerted by them are acting horizontally, the transformation of the forceacting direction from horizontal to vertical being carried out by means of a rack and pinion gear or a bolt and nut connection.

The stroke of the hydraulic jacks used for raising the sliding mold is for practical reasons generally limited to a certain constant value. It is then necessary to match the stroke of the hydraulic apparatus acting horizontally, so that the ratio between the two strokes corresponds to the desired slope of the concrete structure.

One object of the present invention is to provide a scaffold system in which the ratio between the strokes of the means acting horizontally and vertically can be programmed in advance and during progress of the molding operation automatically controlled into agreement with the desired geometric shape of the concrete structure, the scaffold being also, when necessary, in addition thereto subjected to a continously acting biasing force.

A special object of the invention is to provide a scafiold system in which the variation of the size of the scaffold and the biasing thereof may be programmed in advance and automatically controlled without any need of changing the strokes of the horizontally acting members while the molding is in progress.

The main characteristic of a scaffold system satisfying the objects above accounted for is that the system comprises a spoke assembly connected to the scaffold and constituted by substantially regular and horizontally located spoke wires diverging from a central point, and by means for variation of the horizontal shape of the scaffold and of the effective length of the spoke wires in a predetermined relation to the effective stroke of the force means acting vertically so that the predetermined horizontal cross-section of the concrete structure in difierent vertical levels is automatically obtained.

The invention will now be described in greater detail, reference being made to the accompanying drawings, in which:

FIG. 1 is a diagrammatic vertical section view showing a sliding mold yoke mounted between two scaffold units and provided with a telescope mechanism and a spoke assembly.

FIG. 2 is a diagrammatic fragmentary top view showing two sliding mold yokes with an intennediate scaffold unit, telescope mechanism and a spoke system.

FIG. 3 is a diagrammatic vertical view illustrating two sliding mold yokes and an intermediate scaffold unit as viewed from the interior of the concrete structure.

FIG. 4 is a diagrammatic horizontal section through a crossbearn vertically movable along the yoke and supporting the upper portion of the scafi'old unit.

FIG. 5 is a lateral view exemplifying a telescope mechanism.

FIG. 6 relates to the same embodiment as shown in FIG. 5 but is a top view.

FIGS. 70 73 show different cross-sections through the telescope mechanism taken along lines VIIa through VIIg indicated in FIG. 6.

FIGS. 8 12 show the telescope mechanism of FIGS. 5 7 as seen from above and illustrate the racks acting via toothed ratchets on the vertical spindles of the scaffold and the spoke assembly. Also shown is a hydraulic force member connected to the one rack of the telescope mechanism which has been illustrated in difierent operational position defined by programming wedges or templets. FIG. 8 illustrates the telescope mechanism in its basic position before any wedges have been mounted. FIGS. 9 and 10 illustrate the location and operation of the wedges when the force member is exerting a pushing force on the telescope mechanism. FIGS. 11 and 12 illustrate the case in which the force member is exerting a pulling force on the telescope mechanism.

FIGS. 13 15 are diagrammatic views exemplifying vertical cross-sections through concrete structures, FIG. 13 relating to FIGS. 9 and 10, and FIG. 14 to FIGS. 11 and 12. FIG. 15 shows a concrete structure the lower part of which cor responds to FIGS. 9 and 10 whereas its upper part relates to FIGS. 11 and 12.

In FIGS. 1-4 reference numeral 1 relates to a sloping concrete wall erected by means of a sliding mold 2 with a yoke having a pair of vertical legs 3a, a lower fixed cross-beam 3b and an upper fixed cross-beam 30. A movable cross-beam 4 is vertically displaceable along the legs of the yoke by means of sleeves 4a surrounding said legs. The yokes are held in spaced relationship by flexible scaffold units which, according to the embodiment illustrated, are constituted by frames 5a and 5b shaped like pairs of scissors and having their lower ends pivotably connected to the lower fixed cross-beam 3b of the yoke, whereas their upper ends are pivotably connected to the vertically displaceable yoke cross-beam 4. At the outer ends of the cross-beams the left ends are seen in FIG. I the frames are connected over adjustable brackets 3d and M, respectively.

Between the two fixed cross-beams of each yoke there are mounted two axially journaled vertical threaded spindles 6 and 7 carrying nuts 6a and 70 secured to the movable crossbeam. At its top end spindle 6 carries a toothed ratchet 6b and, on top of that, a chain wheel 60. Correspondingly, spindle 7 has at its top end a chain wheel 7c. Those two chain wheels are interconnected by an endless chain 13 provided with a stretching device 13a. The components now described constitute means which upon rotation of spindle 6 displace the movable cross-beam 4 upwards or downwards and, in so doing, alter the vertical positions of the top ends of the scissors 'units connected to that cross-beam whereby those units are laterally shortened or lengthened corresponding to a decrease or an increase of the cross-section of the scafiold system made up by the units.

Numeral 8 designates a threaded spindle similar to the ones above described and carrying a nut 8a slidably guided along a vertical rod 3e secured to the two fixed cross-beams of the yoke. Spindle 8 does at its top end carry a toothed ratchet 8b. The radial spoke wires 9 and 10 extend from central points 9:: and 10a and pass via pulleys 1 l vertically upwards along spindle 8. The wires are secured to the nut 84 by means of locking screws 120. At the lower fixed cross-beam 3b there are additional locking screws 12b. Those are necessary for the stepwise movement of the sliding mold in a manner obvious to those skilled in the art. The details now referred to constitute a device which upon rotation of spindle 8 moves 8a upwards or downwards and, in so doing, shortens and lengthens the horizontal parts of the spoke wires, i.e. decreases or increases the radius of the spoke assembly.

The fixed top cross-beam of the yoke supports a horizontally movable telescope mechanism l4, comprising racks 14a and 15a. Rack 14a is in engagement with the toothed ratchet 6b in which way the scaffold system and rod 15a affect the ratchet 8b and, accordingly, also the spoke assembly. Rack 15a is activated by a force member 16, according to the embodiment shown a hydraulic cylinder, secured to cross-beam 3c and having a piston rod 16b which by bolts 17 is secured to rack 15a. By means of the telescope mechanism including the racks, ratchets and spindles it is possible arbitrarily to vary the cross-section of the concrete structure, i.e. to attain any desired slope of the wall under construction. The telescope mechanism does further include the programming wedges, or templets, l8 and 19, the geometrical shapes of which are determined mathematically in response to the actual conditions. The wedges are attached to the movable cross-beam 4, wedge 18 being horizontally movable such as by means of rollers 180, whereas wedge 19 is rigidly secured to the crossbeam. Wedge 18 passes through a slot in the telecope mechanism, whereas wedge 19 is located at the side thereof. Disregarding the height of the concrete structure the height of the wedges does generally not exceed the distance traveled by cross-beam 4 during its vertical movement between its two extreme positions.

A hydraulic jack 20 is pivotably connected to the lower fixed cross-beam 3b of the yoke in such a way that the jack and the climbing rod 21 may be adjusted to varying slopes.

in the use of the system above described for molding e.g. a concrete structure such as a chimney tapering upwards and of circular cross-section the slope angle of the tangent through a point on any arbitrary level is predetermined and can be defined as a certain ratio between the horizontal and vertical components of the resultant upwards movement of the sliding mold. Accordingly, any given vertical movement of the mold and its scaffold corresponds a predetermined horizontal displacement.Since the stroke of the hydraulic jacks is normally given and constant it is necessary to match the change of length of the spoke wires effected during any such stroke to such a value that the geometrical radius of the scaffold is varied and desired. Normally, the stroke of the jacks is of the order of 1-2 inches.

Let it be assumed that the change of the radial length of the spoke wires is AE, the number of scaffold units N and the tangential length variation of any such unit AR. Then, during one raising operation the total change of the circumference of the concrete structure will be 2 X 1: X A E N X A R, which equation could be written as If the horizontal displacement of racks 15a and 14a caused by force member 16 and corresponding to A E and A R, respectively, is designated H, and H,, then A E K, X H, and A R K,. H,, where K is a factor the amount of which depends of the design of spindle 8 and ratchet 8b, and K, is a factor the amount of which depends on the one hand of the design of spindle 6 and ratchet 6b and, on the other, of the angle between the rods of the individual scaffold units when in their innermost positions. This gives the following equation:

As appears from the above formulas, the traveling distances H and H, of racks 15a and 140 are different for each cycle of operation. Since for practical reasons a scaffold system of the kind here discussed normally comprises at least 8 10 units, which means that N 2 X it, travelling distance H, must be greater than H,. if a bidirectional device is supplied by a common power source the two halves of such a dual device can be programmed to yield predetermined travelling distances and the mutual relationship between those two distances can by mathematical-geometrical calculations be predetermined into agreement with the geometrical shape of the concrete structure under erection.

The device for providing such advanceprogramming and automatic successive change of the horizontal projection of the scaffold system and of corresponding variation of the length of the spoke wires comprises a dual telescope mechanism preferably having two wedge means or templets, permitting continous variation on the one hand of the relative displacement of the two telescoping parts and, on the other, of the horizontal displacement of the complete telescope mechanism relatively to the sliding mold yoke on which it is mounted.

The design principle of the telescope mechanism has been illustrated in FIGS. 5-7. The outer telescopic tube 14 has a rack 14a and the inner telescopic tube 15 has a rack 15a. Those racks are secured inside the tubes. Numerals 14b and 15b designate slots in the respective telescopic tubes each of which does also at its one end have a threaded sleeve 14c and 15c, respectively, permitting variation of the effective length of slots 14a and 15a in response to the actual operational conditions. Numerals 14d and 15d refer to the toothed portions of rods 14a and 15a. The outer telescopic tube 14 does at its one end also have a horizontally projecting stop member He. Wedge 18 is intended to be inserted in slots 14b and 15b and wedge 19 outside the telescopic mechanism so that it can be used to effect the total horizontal displacement of the telescope mechanism by contacting the one or the other side of stop member He see FIGS. 9 and 11.

The purpose of the telescope mechanism and of the programming wedges which are vertically displaceable thanks to their engagement with the movable cross-beam of the yoke is to control and match the horizontal traveling distances of racks 15a and 14a and in that way via ratchets 8b and 61: impart to spindles 8 and 6 a rotational movement the amount of which is selected so that nuts and 6a are caused to carry out the vertical movement corresponding to synchronized changes of the circumferences of the scaffold system and of the length of the spoke wires. The wedges have been given such a geometrical shape that during any given constant cycle of the raising movement effected by the hydraulic jacks the scaffold system and the spoke wires are changed in exact agreement of the predetermined slope of concrete wall 1.

The principle of operation of the system has been illustrated in FIGS. 8 12 wherein line 0-0 illustrate the initial position of the telescope mechanism before insertion of the programming wedges. Line ll indicates the positions of spindles 8 for the spoke wires and line Il-ll the positions of spindles 6 and 7 forming part of the scafiold system. The piston rod 16b of the power member 16 is by means of a bolt 17 connected to rack 15a. The maximum stroke of power member 16 has been designated a. In the initial position shown in FIG. 8 the threaded sleeves 14c and 15c are adjusted so that the effective length of slot 14b is b and so that the right ends of slots 14b and 15b coincide. According to the embodiment illustrated it has been assumed that spindles 6, 7 and 8 all have a right hand thread.

FIGS. 9 12 show the telescope system after insertion of the program wedges 18 and 19. FIGS. 9 and 10 illustrate the mutual positions and operation of the telescope mechanism and the wedges in a concrete structure the vertical cross-section of which appears from FIG. 13 and from the lower part of FIG. 15. FIGS. 11 and 12 illustrate the corresponding condition in a concrete structure the vertical cross-section of which is apparent from FIG. 14 and from the upper part of FIG. 15. In the former case member 16 exerts a pushing force on the telescope mechanism, whereas in the latter case a pulling force exists. In both cases wedge 18 is inserted in the slot 14b, b and attached to the movable cross-beam 4 so that it can be horizontally displaced relatively thereto. Similarly, wedge 19 is in both cases mounted outside and laterally of the telescope mechanism, positioned in slot 19a in the upper fixed cross-beam 3c of the sliding mold yoke. When the cross-section of the concrete structure tapers upwards as shown in FIG. 13 and in the lower part of FIG. 15, wedge 19 is to be mounted to the right of the stop member 14c. When the cross-section increases with increasing height according to FIG. 14 and the upper portion of FIG. 15 wedge 19 is instead mounted to the left of the stop member.

According to FIGS. 9 and 10 in a concrete structure the effective width of wedge 18 at a certain level is c and of wedge 19 d d, e, where d is the distance from line 00 to the right extreme end of slot 190 and e is the effective width of wedge 19. Letter e relates to the position of the telescope mechanism and of the piston 160 with reference to the basic position 0-0. Upon actuation of the power member 16 by supply of hydraulic fluid piston rod 16b is caused to exert a pushing force which during the first cycle moves the rack 15a alone a distance f b-c, whereas rack 14a remains in its initial position. The inner tube 15 of the telescope mechanism will then come into contact with the right hand edge of wedge 18. During the second cycle the movement of power member 16a is continued and via telescopic tube 15 and wedge 18 imparted to the outer telescopic tube 14 and, accordingly, also to rack 14a. The total traveling distance covered by rack 15a is now 3 a-e, i.e. g corresponds to the actual really utilized portion of the maximum stroke of a of the power member as determined by wedge 19. During that second cycle rack 140 has been moved a distance h gf= (a--e) (b-c). 165 It is accordingly realized that for predetermined and constant values of distances a and b which correspond to the maximum stroke and to the effective length of the slot in portion 14 of the telescope mechanism, respectively, the traveling distances g and h covered by rack 15a and 140 are determined by c and e, i.e., by the effective widths of the program wedges at the level of the telescope mechanism. On the basis of mathematical calculations those wedges can be given such a geometrical shape and vertical extension that, at any level, measures 0 and e are selected so that two racks 15a and 14a are imparted exactly that amount of displacement which through clockwise rotation of ratchet 8b and spindle 8 and of ratchet 6b and spindle 6, respectively, shortens the spoke wires and tightens the scaffold system into full agreement with the desired reduction of the horizontal cross-section of the concrete structure.

FIGS. 11 and 12 illustrate an upwardly enlarged concrete structure erected with reliance on the same basic operation of the telescope mechanism and the program wedges as has above been accounted for. In this case power member 16 is exerting a pulling force. During the first cycle of movement rack 15a is moved alone along a distance f 12-1., whereas rack 14a remains in its position. Sleeve 15: of the inner telescope tube is brought into contact with the outer telescope tube 14. During the second cycle the outer telescope tube and, accordingly, also its related rack 14a are displaced by a distance I: g-f. In the final position the total travel of rack 15a is g a-e corresponding to the portion of the maximum stroke a utilized. In a manner analogous with the operation above explained the spoke wires are in this instance lengthened and the scaflold system widened.

When carrying out the invention in practice it is recommended to provide the ratchets above referred to with a simple adjustment device permitting direct switching between right hand and left hand rotation. This eliminates the need of removing and turning those ratchets upon changing the variation of the cross-section of the concrete structure from an increase to a decrease or by vice versa. It is also suitable to provide those adjustment means with an idle position in which anyone of the ratchets in line Il or in line Illl may easily be disconnected thus permitting adjustment of the scaffold system or of the spoke wires.

The pitch of the threads of spindles 8 in line l-l should preferably be greater than the pitch of the thread of spindle 6 and 7 in line IIII due to the fact that normally spindles 8 are to displace their nuts 8a through a longer distance per cycle than what applies to spindle 6 and 7. This makes it possible to reduce the difference in traveling distance of the two racks of the telescope mechanism and in this way to simplify the program wedges.

For the sake of surveyability spindles 6 and 7 have in the foregoing specification and in FIGS. 1, 2 and 4 been assumed to be located at the side of the yoke legs 30. However, in actual practice it is preferred to locate them inside the yoke legs where they are protected from external influence.

It should be emphasized that the invention is applicable to all types of sliding molds as well as to so called climbing molds. In certain applications program wedge 18 can be disposed of and replaced by a separate spacing member inserted in the slot of the telescope mechanism and having a predetermined length c. As the molding proceeds that distance member is at predetermined levels removed and replaced by another such member the length c of which is different. In such a case the change of the scaffold system and of the spoke assembly is controlled solely by the remaining program wedge the geometrical shape of which should then be selected with due attention being paid to the lengths of said spacing members.

What we claim is:

1. A sliding or climbing mold for the erection of concrete structures the horizontal cross-section of which varies vertically, comprising a scaffold system composed by a plurality of flexible scaffold units each consisting of two pivotably interconnected and intersecting rods or the like separated by yokes supporting the mold, the lower ends of said rods being pivotably connected to a cross-beam of the yoke and the upper ends of the rods being pivotably connected to a crossbeam vertically displaceable along the legs of the yoke, the vertical movement of the scaffold system and of the mold being accomplished by means of a first power source substan tially acting in the vertical direction, a second power source acting in the horizontal direction being provided to generate or contribute to the change of the horizontal size of the scaffold system, characterized by a spoke assembly connected to the scafi'old system and consisting of substantially radially and horizontally located spoke wires radiating from a central point and of means for variation of the horizontal shape of the scaffold system and of the effective length of the spoke wires in a predetermined relation to the amount of movement of the vertically acting power source in agreement with the successive variation in the vertical direction of the horizontal cross-section of said concrete structure.

2. A mold as claimed in claim 1, characterized in that said means for variation comprise a number of replaceable templets supported by said vertically movable cross-beam and designed to synchronize the change of the scaffold system with the change of the spoke wires.

3. A mold as claimed in claim 2, characterized by threaded spindles cooperating with the scaffold system and with the spoke wires and provided with nuts, a telescope mechanism being provided for rotation of said spindles and connected to a substantially horizontally acting power source, the total traveling distances of the telescope rods being controlled by means of said templets.

4. A mold as claimed in claim 3, characterized in that said telescope mechanism comprises two telescopic tubes displaceable relatively to each other and each cooperating with a rack in engagement with toothed ratchets acting upon said spindles, the telescopic tubes also having slots for receiving a templet serving to impart movement to the related portion of the telescope mechanism.

5. A mold as claimed in claim 4, characterized in that said templet is substantially horizontally displaceable along a vertically fixed cross-beam, preferably along rollers 6. A mold as claimed in claim 5, characterized in that the outer tube of the telescope mechanism is provided with a stop member for cooperation with a templet attached to said displaceable cross-beam.

7. A mold as claimed in claim 3, characterized in that only one of the of the two vertical spindles cooperating with the scaffold system has a rotatable toothed ratchet, chain wheels and an endless chain being provided for transmitting to said other spindle a uniform and synchronous rotation thereof, said chain preferably being provided with a tightening device.

8. A mold as claimed in claim 1, characterized in that said substantially horizontally acting power source is constituted by a piston and cylinder device having a predetermined stroke maintained constant during change of the dimensions of the scaffold system.

9. A mold as claimed in claim 1, characterized in that said spoke assembly comprises two substantially parallel and horizontal spoke wires for each scaffold system unit, said wires passing over pulleys and connected to the scaffold by locking means for cooperation with a nut in engagement with said spindle, additional locking means being provided for provisional locking of the wires between two consecutive cycles of operation.

10. A mold as claimed in claim 3, characterized in that the pitch of the threads of the spindle acting on the spoke assembly is greater than the pitch of the threads of the spindles cooperating with the scafi'old system.

11. A mold as claimed in claim 4, characterized in that the direction of operation of the ratchets is reversible and that the ratchets can be shifted into a neutral position.

12. A mold as claimed in claim 1, characterized in that said spoke assembly is completely or partially disconnectable from said scaffold system.

F i t t t 

1. A sliding or climbing mold for the erection of concrete structures the horizontal cross-section of which varies vertically, comprising a scaffold system composed by a plurality of flexible scaffold units each consisting of two pivotably interconnected and intersecting rods or the like separated by yokes supporting the mold, the lower ends of said rods being pivotably connected to a cross-beam of the yoke and the upper ends of the rods being pivotably connected to a cross-beam vertically displaceable along the legs of the yoke, the vertical movement of the scaffold system and of the mold being accomplished by means of a first power source substantially acting in the vertical direction, a second power source acting in the horizontal direction being provided to generate or contribute to the change of the horizontal size of the scaffold system, characterized by a spoke assembly connected to the scaffold system and consisting of substantially radially and horizontally located spoke wires radiating from a central point and of means for variation of the horizontal shape of the scaffold system and of the effective length of the spoke wires in a predetermined relation to the amount of movement of the vertically acting power source in agreement with the successive variation in the vertical direction of the horizontal cross-section of said concrete structure.
 2. A mold as claimed in claim 1, characterized in that said means for variation comprise a number of replaceable templets supported by said vertically movable cross-beam and designed to synchronize the change of the scaFfold system with the change of the spoke wires.
 3. A mold as claimed in claim 2, characterized by threaded spindles cooperating with the scaffold system and with the spoke wires and provided with nuts, a telescope mechanism being provided for rotation of said spindles and connected to a substantially horizontally acting power source, the total traveling distances of the telescope rods being controlled by means of said templets.
 4. A mold as claimed in claim 3, characterized in that said telescope mechanism comprises two telescopic tubes displaceable relatively to each other and each cooperating with a rack in engagement with toothed ratchets acting upon said spindles, the telescopic tubes also having slots for receiving a templet serving to impart movement to the related portion of the telescope mechanism.
 5. A mold as claimed in claim 4, characterized in that said templet is substantially horizontally displaceable along a vertically fixed cross-beam, preferably along rollers.
 6. A mold as claimed in claim 5, characterized in that the outer tube of the telescope mechanism is provided with a stop member for cooperation with a templet attached to said displaceable cross-beam.
 7. A mold as claimed in claim 3, characterized in that only one of the of the two vertical spindles cooperating with the scaffold system has a rotatable toothed ratchet, chain wheels and an endless chain being provided for transmitting to said other spindle a uniform and synchronous rotation thereof, said chain preferably being provided with a tightening device.
 8. A mold as claimed in claim 1, characterized in that said substantially horizontally acting power source is constituted by a piston and cylinder device having a predetermined stroke maintained constant during change of the dimensions of the scaffold system.
 9. A mold as claimed in claim 1, characterized in that said spoke assembly comprises two substantially parallel and horizontal spoke wires for each scaffold system unit, said wires passing over pulleys and connected to the scaffold by locking means for cooperation with a nut in engagement with said spindle, additional locking means being provided for provisional locking of the wires between two consecutive cycles of operation.
 10. A mold as claimed in claim 3, characterized in that the pitch of the threads of the spindle acting on the spoke assembly is greater than the pitch of the threads of the spindles cooperating with the scaffold system.
 11. A mold as claimed in claim 4, characterized in that the direction of operation of the ratchets is reversible and that the ratchets can be shifted into a neutral position.
 12. A mold as claimed in claim 1, characterized in that said spoke assembly is completely or partially disconnectable from said scaffold system. 